• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.250-255
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• 2011

This paper dealt with the design, fabrication and application of a risk voltage measurement system (RVMS) which analyzes the step and touch voltages in electrical grounding systems. The RVMS supply 300 V and 1.4 A in ranges from 40 Hz to 1 kHz as the test power source. A DAQ module having resolution of 400 kS/s and 16 bit is equipped with 7 inputs for measuring voltage and current. Also, a noise elimination algorithm of digital filter was applied to reduce the measurement error caused by external noises as a commercial frequency current. The performance of the RVMS was evaluated by measurement of the step and touch voltage according to the IEEE standard 80 and 81 in a grounding system with a 10 m counterpoise. The result showed that the RVMS analyzes the risk voltage with the error below 5%.

• Current Optics and Photonics
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• v.4 no.6
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• pp.558-565
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• 2020

A wavelength-independent optical sensor based on an asymmetric Mach-Zehnder interferometer (AMZI) is proposed. The optical sensor based on an AMZI is very sensitive to wavelength, and wavelength drift will lead to measurement error. The optical sensor is compensated to reduce its dependence on wavelength. The insensitivity of the optical sensor to wavelength mainly depends on the compensation structure, which is composed of an AMZI cascaded with another AMZI and can compensate the wavelength drift. The influence of wavelength drift on the optical sensor can be counteracted by carefully designing the size parameters of the compensation structure. When the wavelength changes from 1549.9 nm to 1550.1 nm, the error after compensation can be lower than 0.066%. Furthermore, the effect of fabrication tolerance on compensation results is analyzed. The proposed compensation method can also be used to compensate the drift of other parameters such as temperature, and can be applied to the compensation of other interference-based optical devices.

• Journal of the Microelectronics and Packaging Society
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• v.20 no.2
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• pp.23-28
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• 2013

Microlens array as basic element of the optical system have been fabricated with various focal length (mainly with long focal length) depending on the purpose of application. In this paper, the microlens arrays were fabricated for observing fluorescent images within sol-gel. Though the fluorescent signal is very low, the microlens array can help obtaining clear images through extracting the fluorescent light from sol-gel. We fabricated microlens arrays with short focal length, which can extract the light using photoresist thermal reflow method. In the experiment, the diameter of microlens decreased after thermal reflow because the solvent within the photoresist was vaporized. Therefore, to compensate the shape error by this reduction, microlens diameter in photomask was altered and spin-coat recipe of photoresist were modified.

• Journal of Sensor Science and Technology
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• v.8 no.5
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• pp.394-399
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• 1999

An automobile hot-film air flow sensor is deposited with platinum by sputtering method, patterned by photoresisted lift-off method, annealed in $1,000^{\circ}C$ and passivated with PI-2723. The TCR of the fabricated hot-film is about $3500\;ppm/^{\circ}C$. In the experiment, the output voltage of the sensor is in proportional to the fourth power root in the air mass flow range of 300 kg/h. The error in the full flow range is about ${\pm}0.7%$. In the range of air temperature of $-20^{\circ}C{\sim}120^{\circ}C$, the error is about ${\pm}1%$ that is ${\pm}2%$ lower than that of the reference sensor. Therefore, the fabricated hot-film air flow sensor satisfies the specification for automobile. Lower temperature error of the sensor provides to control the precise air/fuel ratio of automobile engine and results in improvement of a fuel mileage and the less amount of toxic gases emitted by automobile.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.41-46
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• 2008

Generally optical components are fabricated by grinding, lapping and polishing processes. Those processes take long time to obtain optical high surface quality. In the case of large optical components, the on-machine measurement is strongly recommended because the workpiece is fragile and difficult to set up for fabricating and measuring. This paper is concerned about a swing-arm mechanism which can be used for on-machine measurement of a surface profile with a sensing probe end-effect, and also for grinding or lapping the surface with a corresponding tool. The measuring accuracy and uncertainty using a swing arm type profilometer have been studied. The experimental results show that this method is useful specially in lapping process with the accuracy of $5{\mu}m$. Those inspection data are provided for correcting the residual figuring error in next processes.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.61-68
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• 2000

In general, the design of membrane structures takes three steps. The first is shape finding analysis which is determination of initial equilibrium geometry with uniform stresses. The second step involve the computation of the stress-deformation to get completed membrane under various load conditions. The third step is to divide the membrane structures into several plan strips from the initial equilibrium states. This procedure is needed because of the initial shape has usually undevelopable curved surface and is called as "cutting patterns generation". By introducing this work, the deformation due to the initial stress is removed and approximate cutting patterns are generated. In this approach, however, material properties is not considered, therefore the error between the design stresses and actual stresses during the fabrication of plan strips should be occurred. In this paper, actual equilibrium shape analysis procedure for HP shape models is presented. The deviations of stresses between the design stresses and actual stresses are estimated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1991.10a
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• pp.29-32
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• 1991

It is well known that the fatigue damage process in composite materials is very complicated due to complex failure mechanisms that comprise debounding, matrix cracking, delamination and fiber splitting of laminates. Therefore, the residual strength, instead of a single dominant crack length, is chosen to describe the criticality of the damage accumulated in the sublaminate. In this study, two models for residual strength degradation established by Yang-Liu and Tanimoto-Ishikawa that are capable of predicting the statistical distribution of both fatigue life and residual strength have been investigated and compared. Statistical methodologies for fatigue life prediction of composite materials have frequently been adopted. However, these are usually based on a simplified probabilistic approach considering only the variation of fatigue test data. The main object of this work is to propose a fatigue reliability analysis model which accounts for the effect of all sources of variation such as fabrication and workmanship, error in the fatigue model, load itself, etc. The proposed model is examined using the previous experimental data of GFRP and it is shown that it can be practically applied for fatigue problems in composite materials.

• Journal of Sensor Science and Technology
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• v.9 no.3
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• pp.190-195
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• 2000

The paper presents the constant temperature digital hot-film anemometer that measures easily a wind velocity at the indoor. The output is linearized using microprocessor and analog-to-digital converter, because the fourth root of the wind velocity is the output voltage of the sensor. The comparison result between fabricated and reference anemometer is less than ${\pm}2%$. In the range of air temperature of $23^{\circ}C{\sim}60^{\circ}C$, the error is about ${\pm}1%$ in wind velocity 10m/sec.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.695-698
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• 2002

Induction heating process is one of the most efficient heating process in terms of temperature control accuracy and heating time saving. In the past study, fabrication process of cellular 6061 alloys by powder metallurgical route and induction heating process was studied. To supplement the framing conditions that studied in past study, effect of induction heating capacity and holding time at foaming temperature were investigated. Under the achieved framing conditions, teamed 6061 alloys were fabricated for variation of foaming temperature, and porosities(%)-foaming temperature curves were obtained by try-error experimental method. Uniaxial compression tests were performed to investigate the relationship between porosities(%) and stress-strain curves of framed 6061 alloy. Also, energy absorption capacity and efficiency were calculated from stress-strain curves to investigated. Moreover, dependence of plateau stress on strain rate was investigated in case of cellular 6061 alloy with low porosities(%)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.229-232
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• 2002

This paper describes the development of robot's finger 3-axis force sensor that detects the Fx, Fy, and Fz simultaneously fur stably grasping an unknown object. In order to safely grasp an unknown object using the robot's fingers, they should detect the force of gripping direction and the force of gravity direction, and perform the force control using the detected farces. The 3-axis force sensor that detects the Fx, Fy, and Fz simultaneously should be used for accurately detecting the weight of an unknown object of gravity direction. Thus, in this paper, robot's finger for stably grasping an unknown object is developed. And, the 3-axis farce sensor that detects the Fx, Fy, and Fz simultaneously fur constructing a robot's finger is newly modeled using several parallel-plate beams, and is fabricated. Also, it is calibrated, and evaluated.